维生素B_(12)催化降解三氯乙烯的碳氯同位素分馏机理  

Carbon and Chlorine Isotope Fractionation Mechanism of Trichloroethylene during Degradation Catalyzed by Vitamin B_(12)

作　　者：韩莉[1,2] 甘义群[1,2] 周爱国[1] 余婷婷[1,2] 

机构地区：[1]中国地质大学环境学院 [2]中国地质大学生物地质与环境地质国家重点实验室,湖北武汉430074

出　　处：《环境科学与技术》2014年第10期131-135,166,共6页Environmental Science & Technology

基　　金：国家自然科学基金项目(41072179)

摘　　要：挥发性氯代烃(volatile chlorinated hydrocarbons,VCHs)是地下水中一类重要的有机污染物,维生素B12是催化VCHs还原脱氯的高效催化剂。该文选取VCHs中典型的污染物三氯乙烯(TCE)作为研究对象,以Ti(Ⅲ)为电子供体,探索不同pH条件下,维生素B12催化TCE还原脱氯过程中碳、氯同位素分馏机理。反应溶液初始pH为7.5~9.0时,其表观一级动力学反应速率系数k值为0.06~0.15 h-1;碳同位素富集系数εC为-1.8‰^-2.4‰,氯同位素富集系数εCl均值为-1.5‰。这说明,pH增大,Ti(Ⅲ)还原势能增大,反应的速率提高;还原脱氯不同反应途径所占份额改变,碳、氯同位素分馏程度变化。碳、氯的单体同位素分析(CSIA)技术可以用来评价地下水氯代烃污染降解程度和效率,结合分析2种元素能够提高污染物修复评价的准确性,同位素富集系数的稳定性研究可为其不同环境条件下的精确评价提供理论依据。Volatile chlorinated hydrocarbons （VCHs） are important organic pollutants in the groundwater, vitamin B12 is found as an efficient catalyst during reduction dechlorination. In this study, typical VCHs contaminant trichloroethylene （TCE） was selected as the object of study and titanium citrate （Ⅲ ） as the electron donor, in order to elucidate the effect of initial pH on carbon and chlorine isotope fractionation mechanism during the catalyzing reductive dechlorination of TCE. A remarkable increase of reduction dechlorination rate with apparent rate constant 0.06-0.15 h^-1 of TCE was observed in experiments with pH changing from 7.5 to 9.0, with carbon isotope enrichment factor of -1.8‰-2.4‰ and mean chlorine isotope enrichment factor of -1.5‰. Result indicates that the potential energy of reduction of Ti （Ⅲ ） increases as the increasing pH, making the faster reaction rate. The changing extent of carbon and chlorine isotope fractionation is attributable to the variable ratio of different reaction patmways. VCHs degradation extent and efficiency in groundwater can be evaluated by compound specific isotope analysis （CSIA） of carbon and chlorine, besides, the combination analysis may even provide a higher accuracy in the repair assessment. Studying the stability of isotope enrichment factor can provide theoretical basis to precise evaluation during different environmental conditions.

关 键 词：TCE 维生素BⅢ碳同位素 氯同位素 地下水 

分 类 号：X132[环境科学与工程—环境科学]